1. Field of the Invention
The present invention relates to a plastics material cap for closing a container and in particular, but not exclusively a closure cap for a screw top bottle.
2. Description of the Prior Art
Conventional plastics material caps for screw top bottles have liners inside the top of the cap to act as seals. When the cap is screwed onto the neck of the bottle, the top of the neck compresses the liner, which seals the bottle. However manufacturing caps with liners of a different material is time consuming and expensive in labour and material. Further, recycling is difficult because of the use of two different types of material. Also in order to obtain a reliable seal, use of the correct material for the liner and adequate attachment of the liner to the cap are crucial for effective sealing.
Recently, improvements have been introduced. In place of the liner, a ring extending down from the inside of the top of the cap can be used. When the cap is screwed onto the bottle, the ring and the top of the neck tightly abut, sealing the bottle. However, the material of the cap cannot be as flexible as that of a liner, therefore the precision of the moulding of the cap is critical. Further, the force with which the cap is applied, that is to say the torque applied by a capping machine or capper, needs to be higher than is the case with a liner in the cap. Increasing the torque can itself introduce unreliability.
European patent application No. 0508668 describes a plastics material cap for closing a container, the cap comprising:
a top and a skirt;
first annular sealing member arranged to abut the inside of a neck of the container and
a second annular sealing member arranged to abut the distal end of the neck of the container,
the first and second members have a common root, whereby abutment of the distal end of the container with second member tends to rotate the first member into firmer contact with the inside of the neck, and
a third annular sealing member arranged to abut the outside of the neck of the container and
means on the skirt for holding the cap in sealing relationship with the container.
Another conventional feature is the inclusion of an anti-tamper band at the bottom of the skirt of the cap. This is connected to the cap by frangible links extending from the skirt to the band. Where, as is conventional, the anti-tamper band includes a continuous internal ridge, which rides over and engages under a complementary ridge on the bottle, a considerable amount of force and torque must be transmitted by the links to the band. For this the links must be of a certain size. However, making the links large enough to force the ridges over each other can make them too strong to enable easy breaking of the anti-tamper band from the skirt on opening of the bottle.
International patent application No. WO 98/26991 A describes a plastics material cap for closing a container, the cap comprising:
a top and a skirt;
means integrally formed with the top on its inside for sealing the cap to the container;
means on the skirt for holding the cap in sealing relationship with the container; and
an anti-tamper band frangibly connected to the skirt, the band having
a plurality of upwardly directed tongues resiliently mounted on the band for engagement under a rim on the container on fitting of the cap to the container.
The object of the invention is to provide an improved closure cap.
According to a first aspect of the invention there is provided a plastics material cap for closing a container, the cap comprising:
a top and a skirt;
a first annular sealing member arranged to abut the inside of a neck of the container and
a second annular sealing member arranged to abut the distal end of the neck of the container,
the first and second members have a common root, whereby abutment of the distal end of the container with second member tends to rotate the first member into firmer contact with the inside of the neck, and
a third annular sealing member arranged to abut the outside of the neck of the container and
means on the skirt for holding the cap in sealing relationship with the container;
wherein:
the three annular sealing members depend from the top of the cap;
wherein:
the three annular sealing members are lips dimensioned for slight deflection on sealing abutment with container and adapted to deflect against the bottle under pressure of fluid to be sealed,
the first sealing lip extending transversely of the top of the cap from the common root,
the second sealing lip extending obliquely towards the skirt of the cap from the common root and
the third sealing lip extending transversely of the top of the cap;
wherein:
the sealing lips are of substantially the same cross-sectional shape, being in cross-section:
substantially uniform thickness lips, with
rounded sealing edges.
Whilst it can be envisaged that the means for holding the cap in position can be a snap fit of a feature on the skirt onto a feature on the neck, preferably the means for holding the cap in its sealing position is a screw thread in the cap for co-operation with a screw thread on the bottle.
Normally, the skirt will be provided with an anti-tamper band.
According to another aspect of the invention there is provided a plastics material cap for closing a container, the cap comprising:
a top and a skirt;
means integrally formed with the top on its inside for sealing the cap to the container;
means on the skirt for holding the cap in sealing relationship with the container; and
an anti-tamper band frangibly connected to the skirt, the band having
a plurality of upwardly directed tongues resiliently mounted on the band for engagement under a rim on the container on fitting of the cap to the container
wherein there are also provided
invert V fold members between and interconnecting the tongues;
ribs on the radially outer surfaces of the tongues for limiting the radial movement of tongues on fitting of the cap to the container; and
a ridge on the inside surface of the skirt for co-operating with the ribs in limiting radial movement of the tongues.
Preferably the cap holding means is a screw thread in the skirt for threadedly engaging a complementary thread on the container.
Preferably the sealing means is means integrally formed with the top on its inside for sealing the cap to the container, the sealing means being in accordance with the first aspect of the invention.